It is well known that when a firearm is discharged, jets of gas are formed within the barrel muzzle due to the expansion of gases upon detonation of the cartridge. Additionally, jets of gas are also formed as the bullet is propelled forward through the barrel, caused by the compression of gases in front of the bullet as it moves forward. Flash is caused by the incomplete combustion of gases as they exhaust from the barrel. Specifically, when a weapon is fired, the gases released are typically still burning when they exhaust from the barrel. As such, a “flash” of light can commonly be seen as these gases dissipate and burn off. Muzzle blast (sound) is caused by a shockwave exiting the weapon's barrel. It is also known that turbulence of the hot gases in the chamber of a silencer also increases the dwell time of the gases within the silencer, allowing the further combustion of gases. Accordingly, when these gases exit the gun silencer the amount of flash is reduced.
As technical advances in the firearm silencer industry increase, competition for greater effectiveness in smaller silencer systems has also increased. The area where propellant gas release pressure (and discharge noise) is the highest resides at the muzzle of a barrel, in the rearmost portion of a silencer. Any release of gas that exceeds the speed of sound (roughly 1,100 feet per second, or FPS) will make a loud sound (sonic crack) as the gas is released into the atmosphere. Under some conditions the sound can be heard up to four miles away. The speed of released gases from typical U.S. military rifles (0.223 and 0.308) is roughly 16,000 FPS, well beyond the speed of sound.
One of the common difficulties with silencers is a phenomenon called first round pop wherein the first shot in a series will be notably louder than the rest. This occurs because oxygen in the air (air is roughly 20% oxygen) within a silencer body will combine with superheated, unburned gaseous components in hot propellant discharge and reignite, causing a report that is significantly louder than subsequent reports from shots fired within a following minute or two. In a military setting the first shot should be the most quiet, not the loudest.
Pressure at the muzzle of some firearms can reach 20,000 PSI (pounds per square inch), at which point the propellant gas tends to behave more like a liquid than like a gas. The gas has increased weight and velocity, like a moving liquid under high pressure, but it also expands, like a gas. Propellant gas which is released at a firearm's muzzle also produces an electrical event, where billions of free electrons are suddenly released into the atmosphere, causing a visible flash. The propellant gas release also emits a strong burst of electrical energy and a powerful burst of radio waves. The visible flash of light is enhanced when hot, ionized propellant gas mixes its flame front with free oxygen in air, allowing unburned combustion products to reignite.
Once the propellant gases have slowed below 1,100 FPS their lessened release velocity will not cause a loud sound or sonic crack. A visible flash of light may not be totally extinguished, but it will be greatly diminished with an effective baffling system within the silencer chamber. What is needed is a more effective way to turbinate (spin rapidly, in a volute curve) the released propellant gases within the confines of a silencer's shell or container, and to capture and slow the release of propellant gases into the atmosphere to prevent a sonic crack and visible flash. This should be accomplished in such a way that will allow the use of smaller silencers compared to the size of silencers presently required to reduce sound and flash.